Unraveling the Role of Triplet-Triplet Annihilation and Photodegradation in Difluoroboron-Based Organic Laser Gain Materials.

In this study, we investigate the triplet exciton dynamics of a series of difluoroboron-based organic gain molecules. We synthesized three previously reported molecules from the difluoroboron family and examined their photophysical properties using time-resolved emission spectroscopy and high-level theoretical calculations. Our results reveal that emission from these materials arises predominantly from the singlet manifold via prompt and triplet-triplet annihilation (TTA)-driven delayed fluorescence, rather than from phosphorescence, challenging the earlier assumptions of amplified spontaneous emission (ASE) originating from the triplet manifold. In highly concentrated solutions, the emission shows strong resemblance to that of the crystalline phase, confirming its origin from aggregate singlet states rather than monomeric pathways. Further, the materials are prone to photodegradation, which gives rise to new high-energy fluorescence and phosphorescence bands adding to the complexity of the photophysics of this family of materials.